Reproducing old machines with newer technology

Rod Smallwood rodsmallwood52 at
Tue Jul 14 13:42:47 CDT 2015

Back at a more general level. To my way of thinking what Bob Supnik did 
in software can be extended by producing a hardware replica vehicle for 
his code to give the illusion that the original system has been 
recreated. A sort of machine Turing test if you will.

Rod Smallwood

/On 14/07/2015 19:26, Chuck Guzis wrote://
> On 07/14/2015 10:55 AM, Noel Chiappa wrote:
>> I guess I don't know the 6600 that well (I have the book, and have 
>> skimmed it
>> in the past). What are the novel features in the 6600 that were widely
>> adopted by other machines? (I listed the Atlas because of paging, and 
>> the 801
>> because of RISC.)
> There are more than a few folks who call the CDC 6000 one of the first 
> RISC machines.  In particular, the 6600 with its instruction 
> scheduling and reservation control, multiple functional units, 
> instruction cache, etc. was quite noteworthy.   You could easily 
> recognize the earmarks of a very different machine of the time. The 
> issues that arose when programming later RISC CPUs made me feel that I 
> was back in familiar territory.
> 3-address architecture, 60 bit ones complement words, with separate 
> sets of registers for addresses and indexing.
> A typical beginning programmer's problem was to write a CPU loop to 
> move non-overlapping fields of words in the shortest amount of time 
> (ECS not available).  The best solution usually involved two words per 
> iteration, with one instruction issue per cycle; bottom of the loop 
> load (to overlap the branch) and top-of-the-loop store.
> Another challenge was to write a routine that could load and store the 
> values of all registers from and to memory.  Not as simple as it sounds.
> For me, one distinguishing feature is that there is no condition code 
> register.  You could branch on a register value being signed or zero, 
> or compare and branch on the values of two index registers.  Thus, the 
> result of an operation was covered by the regular register reservation 
> rules.
> The I/O processors (PPUs) had access to all of CPU memory and 
> essentially were their own world, using a 12-bit instruction set 
> derived from the 160A.  One could also say that the PPUs were only one 
> machine with memory and registers being time-multiplexed to simulate 
> 10 machines.
> --Chuck

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